This application claims a priority from German application 100 63 134.7, filed Dec. 18, 2000, and the contents of that application are incorporated herein by reference.
This invention relates to a spotlight of a type having a curved reflector with a lamp arranged inside a cavity formed by the reflector, with the lamp and the reflector being movable relative to one another in a direction of a main optical axis of the spotlight, and with a converging, or collector, lens arranged in front of the reflector in a direction of light emission.
Although such known generic spotlights have a good luminous efficiency, they are not focusable. The mobility of the lamps in the reflectors are often very limited in these spotlights, and this limited mobility has always served only to find an optimal lamp position at which a most uniform possible light distribution is achieved. When a lamp is outside this optimal position, the generic spotlight supplies a very irregular light distribution with several ring-shaped maximums and minimums in a light intensity distribution. This is the same effect that often occurs with flashlights constructed with a deep, smooth reflector.
According to the state of the art, an attempt has been made to smooth out the irregularities in light distribution in these spotlights by using a corrugated, faceted reflector. However, a directional characteristic of the reflector is lost through such a measure. To correct or alter the light emission characteristics of these generic spotlights, additional collector, or converging, lenses are also used as front lenses, although this entails increased costs for material and labor, because, depending on current lamp settings, the corresponding appropriate front lens must be supplied, selected and used.
Focusable spotlights are also known in the art, but they always operate with shallow, or flat, reflectors, which results in a very poor luminous efficiency, especially at a small light emission angle (spot setting).
It is an object of this invention is to provide a spotlight of the generic type mentioned above, that supplies a high luminous efficiency while at the same time is focusable.
According to principles of this invention, a spotlight of the generic type described above has a dispersive, or diverging, lens arranged between the reflector and the collector lens.
In a spotlight of this invention, the arrangement of a dispersive lens between the reflector and the converging lens is very important. It is only through this dispersive lens in combination with a movable lamp in the reflector cavity that a desired focusability is obtained, while the deep reflector assures a high luminous efficiency. Although a light distribution in focusing the spotlight of this invention is not perfectly uniform, focusing of spotlights with a comparable luminous efficiency was not possible at all in the prior art.
Various advantageous and preferred embodiments of the spotlight of this invention are also disclosed and claimed herein.
In some preferred embodiments, the focusability of the spotlight is improved even further because of expanded relative movement possibilities. These embodiments are particularly very beneficial because with them variations in the light emission angles are achieved through simple mechanical displacement of optical components of the spotlight. This eliminates entirely a time-consuming replacement of the converging, collector, lens for the purpose of altering the light emission angle. In especially preferred embodiments, a very uniform light distribution is achieved, also with a high luminous efficiency, by coordinating non-linearity of the displacements of the reflector, the lamp and the dispersive lens for each spotlight setting.
The reflector structure in another preferred embodiment of the spotlight of this invention assures extremely good beam guidance from a standpoint of uniform illumination of an area to be illuminated at each light emission angle.
The special structures of the converging lens and/or the dispersive lens in the preferred embodiments, according to some embodiments, lead to an inventive spotlight having a very small mass. Such a lightweight spotlight of this invention is especially suitable for use on video cameras, where weight plays a crucial role in handling an entire video camera arrangement.
The special structure of the dispersive lens in one preferred embodiment ensures that an area to be illuminated is illuminated especially uniformly at each angle of light emission. Such a purpose is also served by a special structure of the converging lens in one preferred embodiment of the inventive spotlight.
In one especially-preferred embodiment, the dispersive lens, which is structured in this case as an aspherical lens, can carry out a different function with its central part than with its edge area. For example, it is possible to ensure that the entire diameter of the front lens (converging lens) is illuminated in all positions of the optical system. This is especially advantageous when soft shadow edges are to be produced, so that the spotlight of this invention serves as a type of focusable soft light.